In recent years, high-performance, lightweight materials have been developed for use in automobiles. These materials are in many cases lighter, meet at least the same level of safety, and are in some case stronger. Example high-performance materials are fiber-reinforced composites.
One application for such materials is as a bumper crush member, in some case referred to as a crush can or simply a can. The crush member extends between a primary vehicle structural component, such as a frame rail, and an extended bumper member. The crush member is configured and arranged on the automobile to absorb energy in the event of an impact to the bumper.
Crush members are typically made of metal, such as aluminum. In the future, many automobiles will likely have crush members made of a high-performance material such as a fiber-reinforced composite.
The manner by which crush members made of such a composite absorb impact energy is quite different than the manner by which conventional metal crush members absorb energy. Metal members absorb energy by folding and/or pleating.
Now turning to the figures, and more particularly to the first figure, FIG. 1 shows a metal member 10 pleating to absorb energy in an impact event. The impact force in the example of FIG. 1 is coming from the right of the figure, as indicated by an arrow marked by reference numeral 12.
By the failure mechanism of metal members (folding and/or pleating), a crush zone 14 is created. If the crush can does not completely fail, the member will retain a generally unaffected zone 16, adjacent the crush zone 14. Although the crush zone can have different lengths 18, depending on a configuration of the bumper system, including materials thereof, and characteristics of the impact (e.g., direction(s) and magnitude(s) of force(s)), in many instances the length 18A of the crush zone will be less than one inch and can in some cases be a few centimeters.
FIG. 2 shows schematically the same crush member 10 of FIG. 1 installed as part of a bumper system 20 prior to an impact event. The bumper system 20 includes at least the crush member 10 and can be considered to include one or both of a bumper 22 and a primary frame structure 24, such as a front vehicle rail. The crush member 10 connects the bumper 22 to the frame structure 24. The bumper 22 can be, for example, an aluminum extrusion bumper beam.
FIG. 3 shows the system 20 of FIG. 2 immediately following an impact event involving an impact force 12 applied, from right to left in the figure, to the bumper 22. The impact force 12 can result from the automobile contacting an object, such as another vehicle or street-side pole, at the location of the bumper 22.
As shown, the failure mechanism of the metal crush member 10 is to pleat as well as fold or bend (note the bending downward). As also shown, the crush member 10 can stay connected to the bumper 22, thus keeping the bumper 22 connected to the frame structure 24.
Composite members, on the other hand, absorb energy by more significant structural changes, such as by fragmenting and/or splaying, the latter possibly including peeling away/outward in the crush zone, forming fronds. A composite member having a polymeric resin or matrix, for example, can micro-fracture into tiny bits during failure. Some of the fibers may break off and, commonly, fibers will bend away or splay from the primary input force (e.g., the force 12 in FIG. 2.
FIG. 4 shows a first composite member 40 splaying and fragmenting to absorb energy. The impact force in the example of FIG. 4 is also coming from the right of the figure and indicated by an arrow 12.
FIG. 4 shows a crush zone 44 formed by the fragmenting failure mechanism. Although the crush zone 44 for such members 40 can have other lengths 48, depending on a configuration of the bumper system (e.g., materials thereof, dimensions of the member 40, and characteristics of the impact (e.g., direction(s) and magnitude(s)), the length 48 is in some embodiments expected to in many cases be up to about two inches, or more. In some embodiments, the length 48 is up to as much as about eight to about ten inches, or even more.
FIG. 5 shows two schematic images of the crush member 40 of FIG. 4 installed as part of a bumper system 50. The first, top, image shows the bumper system 50 prior to an impact event and the second, bottom, image shows the system immediately following the impact.
The bumper system 50 includes at least the crush member 40 and can be considered to include one or both of the bumper 24 and the primary frame structure 26, such as a front vehicle rail. The crush member 40 connects the bumper 24 to the frame structure 26. As shown, the crush member 40 fails in response to the impact, such as by fragmenting.
By their particular failure mechanisms, such as fragmenting or splaying, composite crush members can absorb more energy than metal members and can exhibit a greater crush distance, while taking up about the same or less space as conventional metal crush members. For instance, fiber-reinforced composites have been found in some cases to have a specific energy absorption of about two, three, or even up to five or more times that of metal members.
Though the failure behavior allows for greater energy absorption and crush distance, the behavior destroys or otherwise disables initial attachment points between the member and the bumper, leaving no structural components keeping the bumper connected to primary automobile frame. The bumper element thus becomes displaced considerably from its original position with respect to the primary automobile frame and in some cases could fall off of the vehicle completely.
As also shown in FIG. 5, the failure of the crush member 40 causes a disconnect between the crush member 40 and the bumper 24. The bumper 24 is thus disconnected from the frame structure 26 and may fall away from the bumper system 40, as shown by an arrow 52 in FIG. 5.
Disconnection of the bumper from the frame presents multiple challenges. One is that the bumper could fall or otherwise move out of place, to a position where it cannot absorb additional energy in the event of another impact. As another, a completely detached bumper could conceivably be a hazard.
There is thus a need for a system that maintains a connection between a bumper element and a primary frame member upon failure of a composite bumper member previously connecting the bumper and frame.